<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 实现原理
        1.需要两个盒子
        2.一个三角形 一个矩形(矩形给宽高,和圆角)
        3.两个盒子浮动 调位置
         */
        div {
            float: left;
            width: 0;
            height: 0;
            border-top: 40px solid transparent;
            border-right: 80px solid red;
            border-bottom: 40px solid transparent;
            margin-top: 50px;
        }

        p {
            float: left;
            width: 200px;
            height: 150px;
            background-color: red;
            border-radius: 20px;
        }
    </style>
</head>

<body>
    <div></div>
    <p></p>
</body>

</html>